1. Technical Field of the Invention
This invention relates to devices for preventing the foam and froth that surges out of a gas propelled liquid container, or from a system using a mechanical pump, when the liquid supply is depleted, from passing into the distribution lines of the dispensing system to which it is attached. This invention relates more particularly to a foam trap, or FOB as it may be called, for keeping the froth from a near-empty beer keg or the like from entering the dispensing lines that carry the beverage to the tap.
2. Background Art
Beer and other carbonated beverages, when poured carefully into a glass or mug for an individual serving, generate a natural head of foam that, when not excessive, tends to enhance the presentation and taste of the beverage for the consumer. In a commercial setting such as a restaurant or tavern, the beer is dispensed from a "remote" beer dispensing system.
To transport the beer from the cooler to the point of dispensing, the beer travels through a beer conduit, an insulated bundle of beer lines and coolant lines. The beer is typically propelled by gas pressure applied over the beer in the keg. The keg is said to "kick" as it empties, when the level of the liquid beer falls below the discharge outlet in the keg. When this occurs, a frothy mixture of propellant gas and residual beer are blown out through the beer lines or hoses. When this happens, it causes at best an erratic, unsatisfactory, gassy pour of the residue that is difficult or impossible to control at the tap. To resume satisfactory dispensing of liquid beer, the lines must be repacked, refilled with beer and the gas displaced.
Various designs of foam traps or FOBs as they may be called, are presently in commercial use to prevent the entrance of excessive foam into the distribution lines as the keg hits empty, with shutoff valves that hold the liquid in the lines while the empty keg is being replaced or the system is being switched to an already connected next keg. The prior art of Francisco Moreno Barbosa, as expressed in UK Patent GB2286581 is instructive, as are the examples of commercial products accompanying this application. Most devices use a float to seal the outlet of a reservoir to which the beer lines are attached when the level of liquid in the reservoir falls low. There is an alternate device that operates on a fluid momentum theory, gas versus liquid. All have inherent problems with cost, operation, sanitation, reliability or maintenance.
There are many commercial and industrial processes that use gas-propelled liquid pumping or dispensing systems, where it is likewise desirable to prevent or control the amount of foam entering the distribution lines. Liquid dispensing systems using vented containers and mechanical pumps are also subject to the same problem, when the liquid level in a vented tank or container falls to level of the outflow port or suction tube so that air is being sucked into the pump along with the residual liquid.